Python developer - coverage question hard

hard.py

import random
import urllib2

import requests


THRESHOLD = 0.3


def randomizer():
    """Chaos monkey, returning special value to be added to content size"""
    if random.random() < THRESHOLD:
        raise NotImplementedError
    return random.randint(1, 10)


class Website(object):
    """Holds information about given website (as URL)"""
    url = None
    status = None
    content_size = None

    def __init__(self, url):
        self.url = url

    def download(self):
        """Fetches various information about the website"""
        special_value = randomizer()
        request = urllib2.Request(self.url)
        try:
            response = urllib2.urlopen(request)
        except urllib2.HTTPError as e:
            self.status = e.code
            return
        self.status = response.code
        content_size = 0
        for char in response.read():
            content_size += 1
        self.content_size = content_size + special_value


class Obtainer(object):
    """Utility helping with various tasks related to downloading"""
    @classmethod
    def get_urls():
        """Returns list of URLs that need to be checked"""
        response = requests.get('http://test.stxnext.local/urls.txt')
        return response.json()


def fetch_all(obtainer):
    """Checks bunch of websites

    Returns list of status codes.
    """
    websites = []
    for url in obtainer.get_urls():
        website = Website(url)
        websites.append(website)
        website.download()
    return [w.code for w in websites]